muscular system Ai generated

articulations(joints)- where 2 bones interconnect

  • bones are relatively inflexible so necessary to allow movement

  • reflect compromise between the need for strength verses the need for mobility

A. three functional categories

  1. synarthrosis- no movement

    ex: sutures and gomphosis (teeth to mandible)

  2. amphiarthrosis -little movement

    ex: symphysis & sendesmosis

    • synarthrotic and amphiarthrotic joints- relatively simple structure

  3. diarthrosis- free movement

    ex: synovial (long bones in upper and lower bones)

    • complex in structure

symphysis- cartilage between 2 pubic bones

syndesmosis- ligament between tibia and fibula

Lt1- synovial joints are freely moveable diatheses containing synovial fluid components of synovial joints (greatest ROM)

A. articular cartilages

  1. resemble hyaline cartilages- matrix contains mire water cimparatively

  2. have no perichondrium

  3. slick and smooth, to reduce friction

  4. are separated by thin film of synovial fluid

B. synovial fluid

  1. similar in composition to group substances

  2. produced at the synovial membrane

  3. circulates from areolar tissue to joint cavity

  4. percolates through articular cartilages

C. joint capsule

  1. dense and fibrous

  2. may be reinforces with accessory structures (tendons & ligaments)

  3. continuous with periosteum of each bone  

II Function of synovial fluid

A. lubrication- with articular cartilage compression, synovial fluid is squeezed out and reduces friction between moving surfaces

B. nutrient distribution- provide nutrients and O2 ad well as waste disposal for the chondrocytes of articular cartilages

  • compression and expansion of articular cartilages pump synovial fluid in and out of cartilage matrix

C. shock absorption- distributes compression forces across articular surfaces and outward to joint capsule

III Accessory structures- provide support and additional stability

  • not all are included in every joint- most are seen in the knee

  1. accessory structures in the knee

    • tendons of quadriceps- pass across joint

    • limit movement & provide mechanical support

A. Bursa (a pouch)- small pocket filled with synovial fluid

  • often form in areas where tendon or ligament rub against other tissues

  • reduce friction and act as shock absorbers

B. fat pads- adipose tissue covered by synovial fluid

  • protect articular cartilages

  • act as packing material for joint

C. meniscus (a crescent)- pad of fibrous cartilage between bones

D. accessory ligaments- strengthen and support

  1. intrinsic ligaments- localized thickening of joint capsule

    ex: capsular ligament

  2. extrinsic ligaments- separate from joint capsule

    • may pass inside (intracapsular) or outside (extra-capsular) the joint capsule

    • intracapsular example: cruciate ligaments

    • extra-capsular example: patellar ligaments


LT 5- arrangement of fascicles (bundles of muscle cells) in the various types of muscles

I Fascicle organization

A. parallel muscle

ex: biceps brachii

  • fascicles parallel to muscle long axis

  • most skeletal muscles in the body are parallel

  • some flat with broad attachments (aponeurosis), or pump and cylindrical with tendon attachments

  • muscle has central body (belly)

  • can contract until shortened about 30% (due to fiber shortening)

B. convergent muscle

ex: pectoralis major

  • fascicles extending over broad area coverage on common attachment site

  • versatile action

  • different portions can contract to produce different actions

  • pulls less on attachment compared to parallel

C. Pennate muscle (penna, feather)

  • fascicles form common angle with tendon

  • pull at an angle on the tendon

  • shorter movement of tendon verses parallel

  • contains more fibers than parallel of same size= more tension

three types

  1. unipennate- all fibers on one side on tendon

ex: extensor digitorum

  1. Bipennate- fibers insert on both sides of tendon

    ex: rectus femorus

  2. multipennate- tendon branches within pennate muscle

    ex: deltoid

D. sphincter muscle= circular muscle

ex: orbicularis oris


LT 6- the name of a muscle can help identify its location, appearance, or function

I individual muscle parts

A. Origin- fixed attachment